May L T, Neta R, Moldawer L L, Kenney J S, Patel K, Sehgal P B
Department of Microbiology and Immunology, New York Medical College, Valhalla 10595.
J Immunol. 1993 Sep 15;151(6):3225-36.
In the baboon or the mouse, a stimulus such as LPS, TNF, or IL-1 typically led to a rapid induction of circulating IL-6, the levels peaked by 2 to 3 h and then declined to near-baseline values by 6 to 8 h. Administration to baboons or mice of "neutralizing" anti-IL-6 mAb followed by an IL-6 inducer led to a marked and sustained increase in circulating IL-6 levels. IL-6 Ag, IL-6 biologic activity, neutralizing anti-IL-6 mAb, and IL-6/anti-IL-6-mAb complexes could all be observed for an extended period of time (beyond 8 h) in the circulation of such animals. Nevertheless, in mice, if the anti-IL-6 mAb had been administered before the IL-6 inducer, there was a reduction in the in vivo IL-6-induced stimulation of fibrinogen levels, indicating that most of the intravascular IL-6 was not readily available for eliciting hepatocyte effects under these experimental conditions. Intraperitoneal administration into mice of mixtures of murine rIL-6 or human rIL-6 together with their respective anti-IL-6 mAb led to a marked increase in the appearance and longevity in the peripheral circulation of the exogenously administered murine or human rIL-6 species in a biologically active form. Varying the ratio of human rIL-6 to anti-human IL-6 mAb indicated that a molar ratio of 1:1 was sufficient for the ability of mAb to chaperone IL-6 in the murine circulation. Human rIL-6 mixed with "neutralizing" mAb in the approximate ratio 1:1 elicited an enhanced fibrinogen response in vivo in the mouse; an IL-6:mAb ratio of 1:125 led to a reduction in the fibrinogen response even though the levels of circulating B9 bioactivity and of human rIL-6-Ag were maximal under these conditions. Gel-filtration chromatographic and Western blotting analyses of IL-6 present in vivo in the mAb-free baboon revealed that although the IL-6 Ag was largely present in high molecular mass complexes of size 400 kDa in association with soluble IL-6 receptor, the B9 bioactivity was largely of low molecular mass (20 kDa). In contrast, in the anti-IL-6 mAb-treated baboon or mouse, the IL-6 Ag and bioactivity were both largely in complexes of 200 kDa. Thus, the binding of IL-6 in the intravascular compartment to other proteins, anti-IL-6 mAb in the present studies, gives IL-6 unexpected biochemical and pharmacologic properties in vivo.
在狒狒或小鼠中，诸如脂多糖（LPS）、肿瘤坏死因子（TNF）或白细胞介素 -1（IL -1）等刺激通常会迅速诱导循环中的白细胞介素 -6（IL -6）升高，其水平在2至3小时达到峰值，然后在6至8小时降至接近基线值。给狒狒或小鼠注射“中和性”抗IL -6单克隆抗体（mAb），随后给予IL -6诱导剂，会导致循环中IL -6水平显著且持续升高。在这些动物的循环中，IL -6抗原、IL -6生物活性、中和性抗IL -6 mAb以及IL -6/抗IL -6 - mAb复合物都能在较长时间（超过8小时）内被观察到。然而，在小鼠中，如果在IL -6诱导剂之前给予抗IL -6 mAb，体内IL -6诱导的纤维蛋白原水平刺激会降低，这表明在这些实验条件下，大多数血管内的IL -6不易用于引发肝细胞效应。将小鼠重组IL -6（rIL -6）或人重组IL -6与其各自的抗IL -6 mAb混合物腹腔注射到小鼠体内，会导致外源性给予的具有生物活性形式的小鼠或人rIL -6在周围循环中的出现和持续时间显著增加。改变人rIL -6与抗人IL -6 mAb的比例表明，1:1的摩尔比足以使mAb在小鼠循环中陪伴IL -6。以大约1:1的比例与人“中和性”mAb混合的人rIL -6在小鼠体内引发了增强的纤维蛋白原反应；即使在这些条件下循环中的B9生物活性和人rIL -6 - 抗原水平最高，IL -6:mAb比例为1:125时纤维蛋白原反应仍会降低。对未使用mAb的狒狒体内存在的IL -6进行凝胶过滤色谱和蛋白质印迹分析表明，虽然IL -6抗原大部分存在于与可溶性IL -6受体结合的400 kDa高分子质量复合物中，但B9生物活性大部分为低分子质量（20 kDa）。相反，在抗IL -6 mAb处理的狒狒或小鼠中，IL -6抗原和生物活性大部分都存在于200 kDa的复合物中。因此在本研究中，血管内隔室中的IL -6与其他蛋白质（抗IL -6 mAb）的结合赋予了IL -6在体内意想不到的生化和药理特性。
